/*
 * Copyright (c) 2007-2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
/*
 * Copyright 1999-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: Variable.java,v 1.2.4.1 2005/09/14 21:24:33 jeffsuttor Exp $
 */
package com.sun.org.apache.xpath.internal.operations;

import javax.xml.transform.TransformerException;

import com.sun.org.apache.xalan.internal.res.XSLMessages;
import com.sun.org.apache.xml.internal.utils.QName;
import com.sun.org.apache.xpath.internal.Expression;
import com.sun.org.apache.xpath.internal.ExpressionOwner;
import com.sun.org.apache.xpath.internal.XPath;
import com.sun.org.apache.xpath.internal.XPathContext;
import com.sun.org.apache.xpath.internal.XPathVisitor;
import com.sun.org.apache.xpath.internal.axes.PathComponent;
import com.sun.org.apache.xpath.internal.axes.WalkerFactory;
import com.sun.org.apache.xpath.internal.objects.XNodeSet;
import com.sun.org.apache.xpath.internal.objects.XObject;
import com.sun.org.apache.xpath.internal.res.XPATHErrorResources;

/**
 * The variable reference expression executer.
 */
public class Variable extends Expression implements PathComponent {
    static final long serialVersionUID = -4334975375609297049L;
    /** Tell if fixupVariables was called.
     *  @serial   */
    private boolean m_fixUpWasCalled = false;

    /** The qualified name of the variable.
     *  @serial   */
    protected QName m_qname;

    /**
     * The index of the variable, which is either an absolute index to a
     * global, or, if higher than the globals area, must be adjusted by adding
     * the offset to the current stack frame.
     */
    protected int m_index;

    /**
     * Set the index for the variable into the stack.  For advanced use only. You
     * must know what you are doing to use this.
     *
     * @param index a global or local index.
     */
    public void setIndex(int index) {
        m_index = index;
    }

    /**
     * Set the index for the variable into the stack.  For advanced use only.
     *
     * @return index a global or local index.
     */
    public int getIndex() {
        return m_index;
    }

    /**
     * Set whether or not this is a global reference.  For advanced use only.
     *
     * @param isGlobal true if this should be a global variable reference.
     */
    public void setIsGlobal(boolean isGlobal) {
        m_isGlobal = isGlobal;
    }

    /**
     * Set the index for the variable into the stack.  For advanced use only.
     *
     * @return true if this should be a global variable reference.
     */
    public boolean getGlobal() {
        return m_isGlobal;
    }

    protected boolean m_isGlobal = false;

    /**
     * This function is used to fixup variables from QNames to stack frame
     * indexes at stylesheet build time.
     * @param vars List of QNames that correspond to variables.  This list
     * should be searched backwards for the first qualified name that
     * corresponds to the variable reference qname.  The position of the
     * QName in the vector from the start of the vector will be its position
     * in the stack frame (but variables above the globalsTop value will need
     * to be offset to the current stack frame).
     */
    public void fixupVariables(java.util.Vector vars, int globalsSize) {
        m_fixUpWasCalled = true;
        int sz = vars.size();

        for (int i = vars.size() - 1; i >= 0; i--) {
            QName qn = (QName) vars.elementAt(i);
            // System.out.println("qn: "+qn);
            if (qn.equals(m_qname)) {

                if (i < globalsSize) {
                    m_isGlobal = true;
                    m_index = i;
                } else {
                    m_index = i - globalsSize;
                }

                return;
            }
        }

        java.lang.String msg = XSLMessages.createXPATHMessage(XPATHErrorResources.ER_COULD_NOT_FIND_VAR, new Object[] { m_qname.toString() });

        TransformerException te = new TransformerException(msg, this);

        throw new com.sun.org.apache.xml.internal.utils.WrappedRuntimeException(te);

    }

    /**
     * Set the qualified name of the variable.
     *
     * @param qname Must be a non-null reference to a qualified name.
     */
    public void setQName(QName qname) {
        m_qname = qname;
    }

    /**
     * Get the qualified name of the variable.
     *
     * @return A non-null reference to a qualified name.
     */
    public QName getQName() {
        return m_qname;
    }

    /**
     * Execute an expression in the XPath runtime context, and return the
     * result of the expression.
     *
     *
     * @param xctxt The XPath runtime context.
     *
     * @return The result of the expression in the form of a <code>XObject</code>.
     *
     * @throws javax.xml.transform.TransformerException if a runtime exception
     *         occurs.
     */
    public XObject execute(XPathContext xctxt) throws javax.xml.transform.TransformerException {
        return execute(xctxt, false);
    }

    /**
     * Dereference the variable, and return the reference value.  Note that lazy
     * evaluation will occur.  If a variable within scope is not found, a warning
     * will be sent to the error listener, and an empty nodeset will be returned.
     *
     *
     * @param xctxt The runtime execution context.
     *
     * @return The evaluated variable, or an empty nodeset if not found.
     *
     * @throws javax.xml.transform.TransformerException
     */
    public XObject execute(XPathContext xctxt, boolean destructiveOK) throws javax.xml.transform.TransformerException {
        com.sun.org.apache.xml.internal.utils.PrefixResolver xprefixResolver = xctxt.getNamespaceContext();

        XObject result;
        // Is the variable fetched always the same?
        // XObject result = xctxt.getVariable(m_qname);
        if (m_fixUpWasCalled) {
            if (m_isGlobal)
                result = xctxt.getVarStack().getGlobalVariable(xctxt, m_index, destructiveOK);
            else
                result = xctxt.getVarStack().getLocalVariable(xctxt, m_index, destructiveOK);
        } else {
            result = xctxt.getVarStack().getVariableOrParam(xctxt, m_qname);
        }

        if (null == result) {
            // This should now never happen...
            warn(xctxt, XPATHErrorResources.WG_ILLEGAL_VARIABLE_REFERENCE, new Object[] { m_qname.getLocalPart() }); //"VariableReference given for variable out "+
            //      (new RuntimeException()).printStackTrace();
            //      error(xctxt, XPATHErrorResources.ER_COULDNOT_GET_VAR_NAMED,
            //            new Object[]{ m_qname.getLocalPart() });  //"Could not get variable named "+varName);

            result = new XNodeSet(xctxt.getDTMManager());
        }

        return result;
        //    }
        //    else
        //    {
        //      // Hack city... big time.  This is needed to evaluate xpaths from extensions,
        //      // pending some bright light going off in my head.  Some sort of callback?
        //      synchronized(this)
        //      {
        //              com.sun.org.apache.xalan.internal.templates.ElemVariable vvar= getElemVariable();
        //              if(null != vvar)
        //              {
        //          m_index = vvar.getIndex();
        //          m_isGlobal = vvar.getIsTopLevel();
        //          m_fixUpWasCalled = true;
        //          return execute(xctxt);
        //              }
        //      }
        //      throw new javax.xml.transform.TransformerException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_VAR_NOT_RESOLVABLE, new Object[]{m_qname.toString()})); //"Variable not resolvable: "+m_qname);
        //    }
    }

    /**
     * Get the XSLT ElemVariable that this sub-expression references.  In order for
     * this to work, the SourceLocator must be the owning ElemTemplateElement.
     * @return The dereference to the ElemVariable, or null if not found.
     */
    // J2SE does not support Xalan interpretive
    /*
    public com.sun.org.apache.xalan.internal.templates.ElemVariable getElemVariable()
    {
    
      // Get the current ElemTemplateElement, and then walk backwards in
      // document order, searching
      // for an xsl:param element or xsl:variable element that matches our
      // qname.  If we reach the top level, use the StylesheetRoot's composed
      // list of top level variables and parameters.
    
      com.sun.org.apache.xalan.internal.templates.ElemVariable vvar = null;
      com.sun.org.apache.xpath.internal.ExpressionNode owner = getExpressionOwner();
    
      if (null != owner && owner instanceof com.sun.org.apache.xalan.internal.templates.ElemTemplateElement)
      {
    
        com.sun.org.apache.xalan.internal.templates.ElemTemplateElement prev =
          (com.sun.org.apache.xalan.internal.templates.ElemTemplateElement) owner;
    
        if (!(prev instanceof com.sun.org.apache.xalan.internal.templates.Stylesheet))
        {
          while ( prev != null && !(prev.getParentNode() instanceof com.sun.org.apache.xalan.internal.templates.Stylesheet) )
          {
            com.sun.org.apache.xalan.internal.templates.ElemTemplateElement savedprev = prev;
    
            while (null != (prev = prev.getPreviousSiblingElem()))
            {
              if(prev instanceof com.sun.org.apache.xalan.internal.templates.ElemVariable)
              {
                vvar = (com.sun.org.apache.xalan.internal.templates.ElemVariable) prev;
    
                if (vvar.getName().equals(m_qname))
                {
                  return vvar;
                }
                vvar = null;
              }
            }
            prev = savedprev.getParentElem();
          }
        }
        if (prev != null)
          vvar = prev.getStylesheetRoot().getVariableOrParamComposed(m_qname);
      }
      return vvar;
    
    }
    */
    /**
     * Tell if this expression returns a stable number that will not change during
     * iterations within the expression.  This is used to determine if a proximity
     * position predicate can indicate that no more searching has to occur.
     *
     *
     * @return true if the expression represents a stable number.
     */
    public boolean isStableNumber() {
        return true;
    }

    /**
     * Get the analysis bits for this walker, as defined in the WalkerFactory.
     * @return One of WalkerFactory#BIT_DESCENDANT, etc.
     */
    public int getAnalysisBits() {

        // J2SE does not support Xalan interpretive
        /*
            com.sun.org.apache.xalan.internal.templates.ElemVariable vvar = getElemVariable();
            if(null != vvar)
            {
                    XPath xpath = vvar.getSelect();
                    if(null != xpath)
                    {
                            Expression expr = xpath.getExpression();
                            if(null != expr && expr instanceof PathComponent)
                            {
                                    return ((PathComponent)expr).getAnalysisBits();
                            }
                    }
            }
        */

        return WalkerFactory.BIT_FILTER;
    }

    /**
     * @see com.sun.org.apache.xpath.internal.XPathVisitable#callVisitors(ExpressionOwner, XPathVisitor)
     */
    public void callVisitors(ExpressionOwner owner, XPathVisitor visitor) {
        visitor.visitVariableRef(owner, this);
    }

    /**
     * @see Expression#deepEquals(Expression)
     */
    public boolean deepEquals(Expression expr) {
        if (!isSameClass(expr))
            return false;

        if (!m_qname.equals(((Variable) expr).m_qname))
            return false;

        // J2SE does not support Xalan interpretive
        /*
            // We have to make sure that the qname really references
            // the same variable element.
        if(getElemVariable() != ((Variable)expr).getElemVariable())
            return false;
            */

        return true;
    }

    static final java.lang.String PSUEDOVARNAMESPACE = "http://xml.apache.org/xalan/psuedovar";

    /**
     * Tell if this is a psuedo variable reference, declared by Xalan instead
     * of by the user.
     */
    public boolean isPsuedoVarRef() {
        java.lang.String ns = m_qname.getNamespaceURI();
        if ((null != ns) && ns.equals(PSUEDOVARNAMESPACE)) {
            if (m_qname.getLocalName().startsWith("#"))
                return true;
        }
        return false;
    }

}
